Preparation Of Monodispersed Spherical Mesoporous Silica Nanomaterials And Its Application In Polyamide Reverse Osmosis Composite Membranes

Reverse osmosis technique has become one of the most effective techniques in thedesalination of seawater. However, the high energy consumption, low selectivity,fouling-prone of the current reverse osmosis membrane make the cost of obtainingfresh water through reverse osmosis technology was still very high. For the tunablehydrophilicity, antimicrobial capability along with better chemical, thermal, andmechanical stability of mesoporous silica, it can be used to prepare mesoporousSiO₂-polyamide thin film nanocomposite reverse osmosis membranes, and aims toimprove the comprehensive performance of traditional polyamide reverse osmosiscomposite membrane.Monodispersed spherical mesoporous silica nanomaterials with different particlesize were synthesized using alkyl trimethyl ammonium bromide （CTAB） as template,ethanol as co-solvent，tetraethylorthosilicate （TEOS） as silica source and sodiumhydroxide as catalyst by modifying st ber method. The materials are characterizedthrough FT-IR, XRD, N₂adsorption/desorption, SEM and TEM. The results indicatedthat the morphology of the materials is spherical, and its with uniform particle sizeand ordered hexagonal mesoporous structure as well as high surface area. Themonodispersity and the mesoporous structure of the materials is better with CTABconcentration of0.0056mol/L, TEOS concentration of0.053mol/L, NaOHconcentration of0.014mol/L, and1/9of ethanol ratio at353K.Monodispersed spherical amino-functionalized mesoporous silica nanomaterialswere synthesized using3-aminopropyltriethoxysilane （APTES） and TEOS as mixedsilicon sources by co-condensation method. The results indicated that this method cansuccessfully introduced amino to mesoporous SiO₂particles, and when the dopingquantity of APTES is10%, it can keep the right amount of amino access, while maintaining the structure of the product ordered.The monodispersed spherical mesoporous SiO₂-polyamide reverse osmosiscomposite membranes were obtained by interfacial polymerization by doping thesynthesized mesoporous silica and amino-functionalized mesoporous silica sphericalparticles. The results indicated that the surface of the reverse osmosis membranesappeared the apparent structure of "peaks and valleys", and spherical paticles arevisible on the membrane surface. EDS confirm that the mesoporous silica and theamino-functionalized mesoprous silica particles has been doped into the film layersuccessfully. The water flux of the modified membranes has been improved nearlytwo times while their solute rejection remains above94%.